Non-thixotropic flour adhesives and methods therefor



Sept. 5, 1961 J. w. HORNER, JR 2,999,028

NON-THIXOTROPIC FLOUR ADHESIVES AND METHODS THEREFOR Filed Sept. 16, 1958 X fr w 0 1 m o o 3 f `o m0 t?, u. o

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ATTORNEY United States Patent O F 2,999,028 NON-THIXOTROPIC FLOUR ADHESIVES AND METHODS THEREFOR James W. Horner, Jr., Minneapolis, Minn., assignor to Daniels-Midland Company, Hennepin, Minn., a dorporation of Delaware Filed Sept. '16, 1958, Ser. No. 761,350 5 Claims. (Cl. 10G-150) l This invention relates to an improvement in flour cor-v rugating and laminating adhesive compositions and the method for preparing non-thixotropic adhesives based principally upon u-ngelatinized cereal hours. More particularly the invention concerns the use of waxy starches or ours in combination with cereal flours preferably with reference to grain sorghum flour and less preferably other cereal and like flour materials, yin overcoming thixotropy and especially providing an improvement in cereal flour corrugating adhesives.

Corrugating adhesives, as presently used in the industry, yare prepared in twoportions, a carrier and a secondary. These portions are then ycombined to give the final adhesive. The carrier generally consists of a viscous aqueous alkaline solution of gelatinized starch. The secondary consists of an aqueous suspension of ungelatinized starch. Cereal our material, in; the secondary, mixed with normal starch 'is thixotropic. This is very evident in the case of corrugating adhesives. When the more economical starchy flours are used in such adhesives in place of corn starch, the resulting adhesives also have disadvantageous properties.

One of the disadvantageous properties manifested by flour-based adhesives is their thixotropic property. Consequently ilours, as such, are not ordinarily practical for corrugating machine operation. In large scale operations this thixotropy causes improper flow and ridging or rippling on the applicator roll. This results in nuneven and wasteful application. Furthermore, the flow of the adhesive in the supply pan is insuicient to properly wet the coating roller to obtain the best application. As indicated, it is recognized that refined starches of reduced, or very low, protein content have heretofore been used in oornigating adhesives. For economic reasons it is very desirable to make use of cereal ours in lieu of starches. Although the fuse of flour by the adhesive industry has been attempted, our has not proven satisfactory as shown by the continued use of starch, and attempts made to modify our material with silicates.

Many types of prepared starches are available for industrial purposes and are regularly used for paper and textile sizes, adhesives, food products, salad dressings, puddings, canned foods, confections, 4and the like. In this case a large variety of product viscosities is possible depending upon the source of the starch, its method of treatment and degree of cooking. Generally, starches in this group are corn, waxy maize, tapioca, Sago, potato, wheat, rice, arrowroot, sorghum and sweet potato. Usually, the corresponding llours from the same sources cannot be used `in place of the starches to achieve the same end use product and/ or properties.

There are cases where waxy starch, especially waxy corn starch, is added to regular corn starch or other starches to act as a stabilizer by reducing their paste viscosities and the tendencies of the regular starch pastes to gel. This is a known fuse for waxy starch. However, such mixtures are not known to be machine operable as corrugating and laminating adhesives.

Thus, it will be recognized that there is a need for making cerealY our materials more directly applicable to corrugating machines.

` Itis therefore an object of this improvement to provide i non-thixotropic adhesives, based on the combination of waxy corn starch with ungelatinized cereal our materialv to overcome and eliminate the above problems with our adhesives.

-It is another object of this improvement to provide .a waxy flour or waxy starchin the carrier portion of a ourbased corrugating adhesive, to reduce the thixotropy and improve the flow characteristics of the adhesive.

It is still another object of this improvement to provide a waxy our or waxy starch in the carrier portion of a corrugating adhesive and to produce a ilour base adhesivey of reduced thixotropy when corn, rice, wheat, oat, rye,

sorghum or other like cereal flours are used in the secondary of the adhesive composition.

To accomplishment of the foregoing and related ends,-

this improvement then comprises the features herein-after more fully described and inherent thereimand as particularly pointed out in the claims. The following description sets forth in ydetail certain illustrative embodiments of the improvement, these being indicative, however, of

but a few of the various ways in which the embodiments of the disclosure may be employed.

The discovery upon which this invention is lbased lies in the use of a powdered waxy material in the form of waxy flour or waxy starch in the carrier portion of the corrugating adhesive, as described, with a ilour material, preferably cereal grain ilours and lessV preferably root flours, in the secondary portion of the said adhesive. This is different than the use of normal gelatinized corn starch with ungelatinized starches as known in this art..V Thus, it has Ibeen discovered that` it is possible to'y produce cereal iiour based corrugating adhesives, with de?y sirable flow characteristics, by utilizing waxy starches and waxy ilours in the carrier and essentially cereal or less preferably root lours in the secondary, as herein described.

For a clarification and understanding of the waxy materials utilized herein, the following differentiation and distinction over ordinary starches and normal flour is submitted. Starch consists of long chains of anhydroglucoseL stantially 100% amylopectin. It is these latter varieties f, which are referred to by the term waxy, -in relationship to the peculiar waxy appearance manifested by the inside of the kernel when it is cut.

The best known waxy variety of substantially J thixotropic with cereal flours, whereas a paste of waxy.

corn starch is clear, uid and cohesive.

The ter-m waxy starches or waxy flours as used herein with reference to the carrier is intended to include waxy corn starch, modied waxy corn starch, whole waxy corn our, waxy sorghum starch,'dehulled degermed waxy sorghum flour, whole waxy sorghum Hour, waxy rice Hour and the like."` When these same ou-rs are used, in the secondary, with a non-waxy component in the carrier, thixotropic adhesives are the expected results.

The term our, as used herein, is generally under-l stood to mean a pulverized product prepared from vegef` tablel material with a minimum amount of separation or',

Patented Sept. 5,- 1961 In one of them, called purification of the constituents. For example, in the preparation of a our from a cereal grain, the amount of separation or purification, if any, usually extends only to the separation and removal of the hull and germ. Ihe constituents of the endosperm, which is pulverized to yield the flour, are not separated. As a result, the our contains characteristic and usual amounts of protein, oil, hemicelluloses and metallic salts. Starch, on the other hand, is prepared from the same vegetable materials by more complex processes which yield products containing only very small amounts, if any, of the non-starch constituents of the original material.

Such our materials are derived from the sources above described for waxy starches and waxy flours and include preferably such other cereal flours as wheat, oat and rye, and less preferably root flours as illustrated by tapioca flour.

To more clearly define this invention, or improvement in cereal our corrugating adhesives, carrier and secondary adhesive compositions, including the method for evaluating thixotropy, within the limits of this improvement, are hereinafter illustrated.

My carrier compositions are formulated within the limits as follows:

Part 1 (carrier): Parts by weight A. Water 97-156 B. Waxy starch or waxy our 24-33 C. Caustic soda (monovalent alkali) 4.9-7.4 D. Water for caustic soda 13-21 E. Cooling water 12S-206 The carrier compositions were prepared by adding the waxy starch or flour, B, to the water, A, contained in a suitable vessel equipped with agitator and heating elements. The caustic soda, C, previously dissolved in the requisite water, D, was added rapidly to the waxy starch or waxy flour slurry while stirring rapidly. At that point the concentration of the caustic soda was high enough to gelatinize the starch or flour, without the application of heat. However, the preferred method is to heat the carrier composition to within the temperature range of 110-180 F. and most preferably to about l45-160 P. for a period of from about 8 to about 2O minutes, and preferably about 15 minutes. Stirring was maintained throughout this heating period. The cooling water, E, was next added rapidly and agitation was continued for minutes more. The carrier was then ready for addition to a secondary as described below.

The function of the caustic soda is to lower the gelatinization temperature of the ungelatinized flour (added via the secondary as described below) to the point where said ungelatinized flour gelatinizes in situ after the adhesive has been applied to the corrugated board and as the corrugated board is subjected to heat in the corrugating machine. Other strong alkalies have the same effect. For example, in place of the caustic soda in the typical carrier formula above, one may use from 6.9 to 10.4 parts of potassium hydroxide.

The secondary was preferably made simultaneously with the carrier. My secondary compositions are formulated within the limits as follows:

Parts by weight F. Water 571-715 G. Borax 4.9-7.4 H. Flour (cereal or root) 193-243 The secondary was prepared by adding the flour, H, to a solution of the borax, G, in the water, F, and agitating until a smooth mixture was obtained.

Next, and with very rapid agitation, the carrier was added slowly to the secondary over a period of about -20 minutes. After both components had been thoroughly mixed, the temperature was noted and the viscosity was determined by the Penick and Ford method. Penick and Ford viscosity is the time (in seconds) required for 100 ml. of the adhesive to flow through an orifice of standard size. Standard instruments for this determination are commonly used in the corrugating industry.

The adhesive was next homogenized by further very vigorously mixing with an Eppenbach mixer for 10 minutes followed by another Penick and Ford viscosity determination. The purpose of the Eppenbach mixing was to simulate, in the laboratory, the vigorous mechanical action applied to a corrugating adhesive in a corrugating plant as it is continuously pumped from a storage tank to the adhesive pans of the corrugating machine and back to the storage tank. The adhesive was now ready for use and further testing.

In the nal adhesive composition, the best results are obtained when there is present about between 10% and 20% of the waxy components based on the solids. In the compounding of the carrier, a portion of the waxy component may be substituted by a non-waxy component. When sorghum flour was used in the secondary and a mixture of waxy corn starch with regular corn starch was used in the carriers, the thixotropy decreased as the percentage of waxy corn starch increased. Some reduction in thixotropy has been observed also when potato starch, tapioca llour and a converted hydroxyethylated starch were used in lieu of the waxy component in the carrier, with a sorghum our in the secondary.

As heretofore indicated, some typical flours which are preferably used, in the secondary portion of the adhesive composition, with a waxy component in the carrier to produce my corrugating laminating adhesives, as described, are e.g. sorghum, corn, n'ce and wheat ours. The nal adhesive solids preferably contains between about and 90% of these ours. The borax component is the preferred material, as it has afforded the best results. However, other borate salts of the di, hypo, meta, ortho-, per, pyro-, and tetra-borates may be used in equivalent workable proportions.

The above description is best illustrated by the following specific examples:

Example l This example represents a non-thixotropic adhesive made according to the typical formula and procedure given above, utilizing whole waxy grain sorghum Hour in the carrier and grain sorghum flour in the secondary.

Part 1 (carrier): Parts by weight The adhesive was prepared by the procedure described above, the carrier being heated at 160 F. for 15 minutes. The Penick and Ford viscosity of the adhesives was 31.9 seconds at F.

'I'he thixotropic property of an adhesive as prepared above can best be measured by the Brookfield viscometer. For example, a sample of this adhesive was placed in an 800 ml. beaker. The spindle was lowered into the adhesive and permitted to rotate one minute at each speed prior to taking readings at 6, 12, 30, 60, 30, 12 and 6 revolutions per minute in that order.

Cycles of Brookfield viscosities were determined, as follows: Y

R.p.m.: Viscosity, poises 6 for 1 min 13.6 12 for l min 10.7 30 for 1 min 7.7 60 for 1 min 6.0 30 for 1 min 7.6 12 for 1 min 9.8' 6 for 1 min 14.0

Alfter the adhesive had stood undisturbed for 15 minutes, Without removing the spindle, the same cycle was repeated, asvfol'lows:

A linal Penick and Ford viscosity determination showed a reading of 33 seconds.

Illustrative and comparative typical Brooklield viscosity p curves of the herein described non-thixotropic adhesives and a conventional type having thixotro-py yare shown in the accompanying drawing. Curve 1 from Example 3 is `typical of `a thixotropic adhesive. At the lower spindle revolution the viscosity appeared to be the highest, approaching a minimum Iat 60 revolutions 'and reaching a maximum as 6 revolutions are again approached. The nonthixotropic adhesives shows a fairly constant viscosity over the same spindle revolutions, as shown by curves 2 and 3 `from Examples land Il, respectively. Thus, it is shown that the desirable properties of the non-thixotropic vehicles can readilybe measured or recorded via the Brookfield visoosities at the several spindle speeds. The straightness, as characterized by curves Zand 3, indicates the relative lack of thixotropity of the adhesive.

The adhesives which have Brookfield viscosities of not over 25 poises `at the beginning and end of the viscosity measurement cycles at 6 revolutions per minute are considered as having the desired non-thixotropy. However, for best results the preferred compositions are those wherein the Brookeld viscosities are not over about l at any spindle speed during the measurement cycle.

Example Il This example illustrates the preparation of Ia non-thixo tropic adhesive based on the use of waxy corn starch in the carrier and grain sorghum dlour in the secondary.

Part 1 (carrier): Parts by weight Water 293.2 Waxy corn starch 24.6 Sodium hydroxide 6.6

Part 2 (secondary): Parts by weight Water 709.3 Grain sorghum flour V ..-209.0 Borax 6.1

The secondary and carrier were prep-ared at the same time.

A slurry `of the secondary components was prepared by simply mixing in `an open vessel equipped with a good agitator.V As soon as the-secondary components were thoroughly mixed the simultaneously prepared carrier was slowly added 'and thoroughly mixed. Further mixing was completed with an Eppenbach mixer ltor l0 minutes.

'Iihe Penick and Ford viscosity at this point was 28.3 seconds at 89 F.

Brookiield viscosities at 84 F. were run by lowering the spindle and running it for one minute lat each speed before recording the viscosity at that spindle speed.

'Ihe viscosity readings were recorded as follows:

Rpm.:

6 lfor 1 min 7 2 12 for 1 min 6.9l 30 for 1 min 5.5 60 for 1 min 4.2 30 yfor l min 5.4 12 for -1 min 7.4l 6 (for l min 8.8

` After allowing the adhesive to stand 15 minutes un-V disturbed (spindle not removed), the same cycle was repeated, las follows:

These data are plotted as curve 3 in the drawing. The straightness indicates lack of thixotropy.

Example III This example illustrates, as a control, the preparation` of a typical thixotropic adhesive based on corn starch in the carrier and sorghum flour in the secondary.

Part 1 (carrier) Water 232.5

Corn starch 13.7

Sodium hydroxide 5.2

Part 2 (secondary):

Water 562.4

Grain sorghum our 181.3k

Borax 4.9

rThe above components -were combined as described in Example 1I. The adhesive had' a Penick and Ford viscosity of 28.8 seconds at 87 F.

The cycle for the Brookield viscosities were as follows:

Second Cycle, polses First Cycle, pulses Rpm. V

y These data are plotted :as curve 1 in the figure. The

U shape indicates thixotropy.

Part 1 (carrier): Parts by weight Water 293.2 Rened waxy sorghum-hour 27.0 Potassium hydroxide 9.3

Viscosity, poisesV Parts by weight'.`

7 8 Part 2 (secondary): The components were combined as described in Exam- Water 709.3 ple II. The adhesive had a Penick and Ford viscosity of Grain sorghum flour 209.0 33.7 seconds at 93 F. The Brookfield viscosities deter- `Borax 6.1 mined the absence of thixotropy within the limits defined. 5 Further beneficial effects on the viscosity characteristics Eglreb? components were combmed as Illustrated m are shown in Table l of comparative data in which a The adhesive had a Penick and Ford viscosity of 27.0 Waxtafd?. of, .Waxy Hour 1S. Sed mfhe Gamer' In seconds at 87 F. the listed adhesives, the carrier contalns between .5%

The cycles for the Brookiield viscosities were as foland 85% of th? Waxy Component (bas'd on total Welght lows. of carrierlwhile the secondary contains between 22% and 25% of a flour (based on total weight of secondary). This range of carrier and secondary components yields ad- R'pm' Frtogeyscle Secosgsycle' hesives with Penick and Ford viscosities of 25 to 45 seconds, depending upon the type of flour. However, 7.0 9.3 Penick and Ford viscosities of 27 to 35 seconds are genjg erally preferred. Embodied inthe examples, as herein de- -g scribed, the water compositions of the corrugating and eo 619 laminating adhesives are formulated and measured at be 7-6 9'0 20 tween about 5% to 25 solids level and by calculation not over about a solids level.

The variations in spindle speed mused only a very The examples in Table 1 vwere prepared by the standard slight variation in viscosity. This indicates the absence procedure of Example II, except that the carriers were of thixotropy. heated to 160 F. instead of to 140 F.

TABLE 1 Thxozropy of flour based adhesives as related zo "waxy" component in the carrier Brookfield Viscosity In Paises Penick & Carrier Secondary Ford Vis- 1st cycle at- 2nd cycle nt- Thixotropy cosity in Sec.

6 r.p.n1. 60 6 r.p.m. 6 r.p.m. 60 6 r.p.m. r.p.m r.p.m

Grain Sorghum Flour Grain Sorghum FlOllr--. 29. 6 63. 0 10. 3 01. 6 79. 5 11. 7 63. 4 Present.

Corn Starch do 32. 2 74.0 12.0 74. 0 97.2 13.5 76. 6 D0,

Waxy Corn Starch. 33.2 19. 0 8.3 20.0 21. 0 9. 0 20.6 Absent.

Amioca l 36. 2 15.0 6. 2 15.4 16. 2 7.1 16. 4 Do.

Whole Waxy Corn F1our 34. 3 21.0 5.3 22. 6 29. 0 9. 4 24.0 D0.

Waxy Sorghum Starch 33. 7 20.0 8. 3 20. 1 30. 0 9. 8 24.0 Do.

Refined Waxy Sorghum Flour 32. 2 17.4 7.0 17.0 18.6 7. 7 17. 4 Do.

Whole Waxy Sorghum Flour-. 33.0 15. 2 6. 5 16. 4 20. 6 8.1 19. 6 D0.

Waxy Rice Flour 32. 3 16.4 6. 5 17. 0 18. 2 7. 4 17.4 Do.

Corn Starch 26. 2 49. 8 7. 7 51.0 57. 6 8.3 45.6 Present Waxy Corn Starch- 25.3 8.0 3. 6 9. 4 10. 6 3.9 8.8 Absent VII Rice Flour 27.0 38. 0 6.7 34.6 50.0 7. 4 34.4 Present XVIII.-... Waxy Corn Starch. 30.0 14.0 6.1 16.0 23. 6 7.4 19.6 Absent XIX Wheat Flour 32. 4 51. 0 21. 5 51.0 55. 6 16. 7 53.4 Present.

X Waxy Corn Starch 27.0 6.0 2.8 6.0 9. 0 1. 9 8.0 Absent 1 Amioca 50 is a modified (by acid hydrolysis or otherwise) waxy corn starch manufactured by National Starch Products, Ine.

Example V This example illustrates the preparation of a non-thixotropic adhesive based on refined waxy sorghum ilour in the carrier and grain sorghum flour plus a small amount of refined waxy sorghum flour in the secondary.

The fiours are commonly supplied in bags containing 100 lbs. of flour. The user wishes to use only whole bags of flour in each batch of adhesive. To do this he adds to the secondary that portion of the 100 lb. bag of waxy flour which is not used in the carrier. In this example the ratio of waxy our to regular Hour is 1 to 5 (i.e., one bag of waxy our to 5 bags of regular our).

Part 1 (carrier): Parts by weight Water 398.0

Refined waxy grain sorghum our 28.6

Sodium hydroxide s 5.2

Part 2 (secondary):

Water 604.3

Borax 6.9

Grain sorghum our 216.7

Refined waxy grain sorghum flour 14.8

An inspection of the Brookfield viscosity data of the various examples in Table 1 reveals at once the beneficial effects produced, in the elimination of thixotropy, by the use of a waxy component in the carrier byicomparing the following examples:

(l) The waxy corn starch in Example VIII vs. corn starch in Example VII.

(2) Whole waxy grain sorghum iiour in Example XIII vs. grain sorghum our in Example VI.

(3) Waxy corn starch in Example XVI vs. corn starch in Example XV.

(4) Waxy corn starch in Example XVIII vs. rice flour in Example XVII; and

(5) Waxy corn starch in Example XX vs. wheat flour in Example XIX.

Illustratively, the corrugating adhesive composition of Example II and other compositions containing the waxy starch and Waxy iiour in the carrier and sorghum our in the secondary were utilized for laminating and bonding corrugated paperboard with a standard corrugating machine, in the manner as described for starch corrugating adhesives in Bauer Patent 2,051,025. During pumping and recirculation the Viscosity of the compositions remained almost constant and a slight change was attributed to evaporation losses. In the stand-ard corrugating machine, operated at speeds up to 400-500 yft. per minute, the adhesive compositions maintained good flow properties and provided a bond comparable to standard starch corrugating adhesives. Further, the vadhesive compositions were utilized to successfully laminate and bond similar and different paper materials and for laminating fabrics.

It will be apparent that many modifications and variations of this invention as hereinafter set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example and invention is limited only by the terms of the appended claims.

I claim:

1. A non-thixotropic corrugating adhesive consisting of about 75-95% water and about 5-25% solids; said solids portion consisting of about 2433 parts of a carricr material selected from the group consisting of gelatinized waxy starches and gelatinized waxy ours consisting essentially of 100% amylopectin, about 19.3-243 parts of an ungelatinized starchy cereal flour, about 4.910.4 parts of a caustic alkali, and about 4.9-7.4 parts of a borate salt.

2. The adhesive of claim 1, in which the carrier material is gelatinized waxy corn starch and the ungelatinized starchy cereal ilour is ungelatinized corn flour.

3. The adhesive of claim 1, in which the carrier material is gelatinized waxy corn starch and the ungelatinized starchy cereal our is ungelatinized sorghum flour.

4. The adhesive of claim 1, in which the carrier material is gelatinizcd waxy sorghum our and the ungelatinized starchy cereal flour is ungelatinized corn our.

5. I'he adhesive of claim 1, in which the carrier material is gelatinized waxy sorghum flour and the ungelatinized starchy cereal flour is ungelatinized sorghum flour.

References Cited in the file of this patent UNITED STATES PATENTS 1,245,984 Satow Nov. 6, 1917 2,212,557 Bauer Aug. 27, 1940 2,419,160 Pierson Apr. 15, 1947 2,610,136 Casey et al. Sept. 9, 1952 2,791,512 Hatch et al. May 7, 1957 2,833,662 Thomas May 6, 1958 OTHER REFERENCES H. H. Schopmeyer et al.: Ind. Eng. Chem., vol. 35, No. 11, pages 1168-1172, 1943.

UNITED STATES PATENT OFFICE CERTIFICATE 0F COBRECTIN Patent No. 2,999vo28 l I septembefe, i961 James Hornerg Jr It is hereby certified that error appears in the above nmbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grantY lines 2 and 3I for VDanel's-Mdland Company,1 of Hennepin7 MinnesotaV a corporation of Delawareq" read Archer-Danels-Midland Company, of Minneapolis,7 Mnnesota1 a corporation of Delawareg line l2 for "Daniels-Midland Company, its successors" read Areher-Daniels-Midland Company,7 its successors in the heading to the printed specgfeatomI lines 45 and Y for "'Daniels-Mdland Compan`yl HennepinQ Minn,V a corporation of Delaware-v' read Areher- Daniels-Midland Company, Minneapolis,I Mnn a corporation of Delawarev Signed and sealed this, 10th day of July 1962;

(SEAL) Attest:

ERNEST W. SWIDER o f DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A NON-THIXOTROPIC CORRUGATING ADHESIVE CONSISTING OF ABOUT 75-95% WATER AND ABOUT 5-25% SOLIDS; SAID SOLIDS PORTION CONSISTING OF ABOUT 24-33 PARTS OF A CAR RIER MATERIAL SELECTED FROM THE GROUP CONSISTING OF GELATINIZED WAXY STARCHES AND AMYLOPECTIN, ABOUT 193-243 PARTS ESSENTIALLY OF 100% AMYLOPECTIN, ABOUT 193-243 PARTS OF AN UNGELATINIZED STARCHY CEREAL FLOUR, ABOUT 4.9-10.4 PARTS OF A CAUSTIC AALKALI, AND ABOUT 4.9-7.4 PARTS OF A BORATE SALT. 